What this lethal rose disease is.
Equally important, how an average gardener may first meet
Rose rosette disease is a virus-like disease of roses that is
becoming more and more common. We'd never heard of it when we first
saw it in a client's garden in 2009 (photos
below). However, when we did our research to determine what the
problem was we found plenty of information dating back to the
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Diagnosing rose rosette disease
The symptoms are definitive. That is, if you see distortion and
discolorations described below you do not need a lab test to
confirm the disease. (Nor could such a test be arranged, as the
disease has not so far or simply cannot be cultured in a lab.).
The carriers (vectors) are eriophyid mites -- microscopic
critters. The mites are in each growing point, visible only with
10x power lens or stronger; if you really want to see them cut open
a distorted bud under a microscope and watch for the mites to
The prognosis is and has been "lethal; usually within 2 years"
and the treatment "remove that whole plant, roots and all,
immediately." It can't be controlled with a miticide.
Symptoms and likely scenario for first sighting
You will probably notice it one spring, if you are unlucky
enough to have it occur in your garden. The new growth on your
roses will be distorted -- some people call it "feathery." The
summer time photos below show the same
distortion in new buds without the red coloration and thickness of
infected growth in the spring. Thorns may grow much more
prolifically than usual, and new branches will "broom." This Rose Rosette Morton Arboretum bulletin is
comprehensive and has very good photos.
If you do what others have done on first seeing this problem,
you'll cut off the strange growth in spring, then watch, hoping
that will take care of the problem. Here's what you may see that
summer, when symptoms may be less noticeable, seem less severe, or
may elude you because the rose has other problems that have become
severe because the plants are weaker.
The photos here were taken in a client's
garden, of a rose which we had under observation after removing a
dozen roses from nearby beds that showed rose rosette symptoms that
spring. We and the client hoped that the infestation was new and
confined to that area of the property where we'd removed roses.
(About 20 roses remained after the purge, all in mixed beds
throughout the property.) The diseased roses were all established
shrubs, some "old" roses, a few hybrid teas. Most had been in the
gardens for a decade, some longer.
We had decided to watch this rose after we cut an unusual amount
of dead wood from it in the same spring we saw rose rosette
elsewhere on the property. It had previously been a very vigorous
plant. We hadn't seen the distinctive new growth distortion of rose
rosette but since it obviously had something wrong we thought it
Source of infection
How did the disease arrive? Probably on a new rose. Since we did
not recall any new roses going in the previous year, the problem
may have been building for two or more years, with symptoms
initially beneath our "radar." The build up may be even slower, or
there is some other way these mites are being moved around. We say
this because we know of three other properties where well
established shrub type roses were suddenly noticed to have rose
rosette disease and where no new roses had been planted for at
least a few years.
Below: A rose we've
removed. Most of the growth produced earlier in the year had died
back. There had been some flowering. The plant kept pushing out new
Below: The distorted appearance of new shoots in summer.
Rose rosette causes the same kind of "featheriness" in spring but
with even more redness than is typical of early spring rose
foliage. The shoots may also be much thicker than usual.
The shrub we'd been watching. (Janet was on camera this day
and does not ever remember to compensate for glare. We apologize
for that fault in the image.) If we had not been looking closely we
might have missed what we show you in the next photos...
...the new growth that's misshapen and smaller than it
should be (below).
Below: Comparing normal size foliage from one part of the
plant to the puny, pale leaves from newer shoots.
Below, left: We might have thought the discoloration was
just a nutrient deficiency. And might not have noticed the dead
wood throughout the plant, all of it very dead. there is a dead
stub in the photo below, and at A in the next photo.
Below: A: Dead wood. B: Earlier growth has been dying back.
C: New shoots are in a witch's broom formation -- too many shoots
together and those lacking rose-orderly fashion. It's a sort of
Check our Forum for current developments or search Extension
publications on the Internet using the terms rose rosette
If you are a Forum participant, please take this article as an
example of how important your posts are on our Forum.
We posted this article when a discussion in our Forum caused us to think
of this possibility and realize we had let over three years slip by
without making a formal report here regarding this disease. We then
created a posting on the Forum specifically for reports of rose rosette disease.